Histopathological Analysis of Elongated Styloid Processes: A New Light on Etiopathogenesis of Eagle's Syndrome

There exists paucity in recorded literature on the detailed microscopic appearance of elongated styloid processes (ESPs) in patients with Eagle's syndrome (ES). Although literature is replete with numerous conflicting and inconclusive theories, the exact cause, mechanism of origin, development and progression of styloid apparatus enlargement remains unclear and ambiguous. To carry out detailed histopathogical examination of excised specimen of ESPs in a patient with ES, with the objective to determine its precise etiomorphogenesis, and to analyse the role of possible triggering factors. Light microscopic examination was carried out of the base, mid- and apical thirds of transorally excised ESPs in a 45-year-old patient with ES. Woven bone trabeculae were found emanating from tendinous insertions of the styloid group of muscles at the mid third of the ESPs. Apical region of the ESPs showed fibro-collagenous mesenchymal tissue with numerous, haphazardly scattered trabeculae of woven bone traversing it. Presence of deeply staining reversal lines all along the length of the ESPs was suggestive of multiple micro-fractures from recurrent traumatic/traction forces, and repeated attempts at repair and ossification. It is proposed that mesenchymal structures composing the stylohyoid ligament at its attachment, and tendinous insertions of styloid muscles into the ESPs are stimulated to undergo metaplastic alterations, by repetitive stress, traction or traumatic stimuli brought to bear upon them, from muscular contractions. This osseous metaplasia of connective cells within them, followed by dystrophic bone deposition, brings about SP thickening and lengthening with their attendant and associated clinico-pathological sequelae.